Messages in this thread | | | Date | Mon, 21 Jan 2002 09:01:56 +0100 | From | Jens Axboe <> | Subject | Re: Linux 2.5.3-pre1-aia1 |
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On Sun, Jan 20 2002, Andre Hedrick wrote: > > No it's not. By your standards, that would mean that if the device is > > setup for 16 sector multi mode, then I could never ever issue requests > > less than that (without doing some crap 'toss away extra data' stuff). > > How else would you handle, eg, 2 sector requests with multi mode set? > > Change the opcode in the command block to single sector, if > rq->current_nr_sectors != drive->multcount.
That crossed my mind too, however that's not what we've been doing in the past and multi mode has worked fine.
> > > The effective operations your changes have created without addressing all > > > the variables is to terminate the command in process. Therefore, the > > > decision made by you was to restrict the transfers to be process to the > > > count in rq->current_nr_sectors. There is no bounds checking based on the > > > command executed. > > > > I'm not stopping a request in progress. I told the drive that the > > request is current_nr_sectors big, so once it finishes transferring > > current_nr_sectors sectors it truly thinks it's really done with that > > request. And it is. However, I'm leaving the request on the queue (or, > > really, ide_end_request is not taking it off because > > end_that_request_first is not indicating it's complete). So I'm simply > > starting from scratch with the remaining data. See? > > I know what you are doing, and I am trying to mate the requirement to use
Yes
> the hardware to what you are sending down. The question you need to > answer is issuing a request for multi-sector transfers less than what the > device is expecting, sane and correct. If you tell me it is correct, > please show me where I read something wrong in the specification.
You are saying that even when I do:
/* this is our request */ rq->nr_sectors = 48; rq->current_nr_sectors = 8;
/* drive->mult_count has been programmed to 16 */
/* bla bla command setup */ OUT_BYTE(rq->current_nr_sectors, IDE_NSECTOR_REG); ide_set_hander(...); OUT_BYTE(WIN_MULTREAD, IDE_COMMAND_REG);
The drive will be wanting to transfer _16_ sectors, even though I told it that I want _8_. This sounds very strange to me, and it means that 2.2/2.4 etc should have never worked in multi mode. I'll go find the spec now... I am just talking out of my ass.
> > > ***************************** > > > The questions to ask "How would the host terminate a command in progress, > > > since BSY=1 (or DRQ=1) at this point? Is that done via a DEVICE_RESET or > > > SRST write?" > > > > [snip] > > > > Moot, there's no premature termination going on. > > >From the OS/HOST side you are 100% correct.
Yep
> >From the device side, do you know that for a fact?
No
> Please read the difference in the two state-machine diagrams, the have the > same name phasing, but each describes which end of the cable you are on > and the expected behavors.
I will do so now, I think I've stated my speculation above and in earlier mails :-)
-- Jens Axboe
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